The present invention relates generally to a computed tomography assembly, and, more particularly to a collimator and scintillator assembly with improved manufacturing costs and accuracy.
Computed tomography has been utilized for a wide variety of imaging applications. One such category of applications is comprised of medical imaging. Although it is known that computed tomography may take on a wide variety of configurations within the medical industry, it commonly is based on the transmission of low energy rays through a body structure. These low energy rays are subsequently received and processed to formulate an image, often three-dimensional, of the body structure that can by analyzed by clinicians as a diagnostic aid.
The reception of the low energy rays, such as gamma-rays, is often accomplished through the use of a device referred to as a scintillator camera. The scintillator camera is typically comprises of a plurality of structures working in concert to-receive and process the incoming energy rays after they have passed through the body structure. A collimator is an element often found in a scintillator camera that is used to limit the direction of photons as they approach the scintillator element. The collimator is commonly used to increase the magnification of a viewed object or control resolution or field of view. Their primary purpose, however, is to control the protons impinging on the scintillator element.
The scintillator element, in turn, is commonly a material with the ability to absorb the protons and convert their energy into light. This allows the low energy rays received by the scintillator camera to be converted into useful information. Scintillator elements may come in a wide variety of forms and may be adapted to receive a wide variety of incoming rays. The light produced by the scintillator element is commonly processed by way of a device such as a light sensitive photodiode which converts the light from the scintillator element into an amplified electronic signal. In this fashion, the information from the scintillator camera can be easily transferred, converted, and processed by electronic modules to facilitate viewing and manipulation by clinicians.
Current manufacturing methodologies for creation of scintillation cameras and the collimator components often present a multitude of challenges. The collimator components often consist of a matrix of tungsten plates in the z-direction and wires in the x-direction. These elements must be aligned with the scintillator and the x-ray focal spot. The height of the collimator elements in the y-direction is critical for scatter rejection. This scenario presents the following challenges: Plate bow along the z-direction is often realized. Alignment of the pack to the collimator in both x and z-directions can be difficult. Focal alignment of the plates can be difficult and costly. Improper manufacturing can result in undesirable sensitivity to focal spot motion.
The plate/wire construction that presents the aforementioned challenges has therefore prompted the development of new manufacturing technologies. Casting of collimator assemblies promises low cost and extensive cast heights. Casting, however, brings these benefits often at the expense of dimensional accuracy from the top to bottom of the casting. Stack laminations, alternatively, may also be utilized as it can provide desired dimensional accuracy. Stack laminations, however, can result undesirable costs in addition to presenting limitations on stack height. Thus each approach can carry with it characteristics that may undermine its use in collimator manufacturing.
It would, however, be highly desirable to have a collimator assembly that utilized the expense and sizing capabilities of cast collimators without suffering from the dimensional accuracy issues. Similarly, it would be highly desirable to have a collimator assembly that utilized the dimensional accuracy of stack collimators without suffering from the expense and height limitations associated with stack manufacturing.